The present invention relates generally to linear beam microwave vacuum amplifier tubes, and it more particularly relates to a multiple cavity klystron for use as a high power amplifier for accelerators and particle colliders, and as a power amplifier for radar, electronic warfare and directed energy applications.
FIG. 1 is a schematic view of a conventional seven-cavity klystron 10. An electron beam 11 is emitted from an electron gun 12. Simultaneously, a microwave signal is fed into an RF input port 14 for interacting with the electron beam 11 within an input resonating cavity 16. The electron beam 11, with velocity modulation superposed by the input microwave signal, passes through a sequence of successive gain cavities 17, 18, 19, 20, 21, where the velocity modulation is amplified, and therefrom through an output cavity 22, where the velocity modulation is converted into an amplified microwave output power and is extracted through the RF output port 24. The spent electron beam is absorbed by the collector 26 positioned after the output cavity.
A plurality of successive drift tubes 30, 31, 32, 33, 34, 35 respectively connect with the cavities 16, 17, 18, 19, 20, 21, 22, such that one drift tube interconnects two adjacent cavities.
In passing through the intermediate cavities 17 through 21, the electrons are subjected to a velocity modulation, retarding them when the RF alternating field through which they pass is at one polarity, and accelerating them on the subsequent half cycle when the alternating field is of the opposite polarity. Accordingly, when the electrons pass into the field-free drift tubes 30 through 35 with differing velocities, they tend to separate into a series of groups or "bunches" moving in space relative to each other. This bunching feature and the spacing between successive cavities are correlated in order to optimize the output power of the klystron.
Examples of conventional klystrons are described in the following representative patents:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 2,605,444 Garbany July 29, 1952 3,195,007 Watson et al. July 13, 1965 3,210,593 Blinn et al. October 5, 1965 3,240,983 Biechler et al. March 15, 1966 3,249,794 Staprans et al. May 3, 1966 3,594,606 Lien July 20, 1971 3,622,834 Lien November 23, 1971 3,688,152 Heynisch et al. August 29, 1972 3,725,721 Levin April 3, 1973 3,775,635 Faillon et al. November 27, 1973 3,811,065 Lien May 14, 1974 3,819,977 Kageyama June 25, 1974 3,902,098 Tanaka et al. August 26, 1975 3,942,066 Kageyama et al. March 2, 1976 4,019,089 Kageyama et al. April 19, 1977 4,100,457 Edgcombe July 11, 1978 4,168,451 Kageyama et al. September 18, 1979 4,216,409 Sato et al. August 5, 1980 4,284,922 Perring et al. August 18, 1981 4,558,258 Miyake December 10, 1985 4,764,710 Frielander August 16, 1988 4,800,322 Symons January 24, 1989 ______________________________________
During the last several years there has been a concerted effort to extend the operation of conventional relativistic klystron amplifiers (RKAs) to higher powers at S-band through X-band. The goal at S-band is to produce a peak output power of 150 MW at a pulse width of 3.0 microseconds, at a pulse repetition rate of 50 Hz. This goal has been achieved. The goal at X-band is the generation of 100 MW at a pulse width of 1.0 microsecond, at a center frequency of 11.424 GHz, at a repetition rate of 100 Hz. To date, the most optimal result achieved so far has been a peak power of 50 MW at a pulse width of 1.0 microsecond at 11.424 GHz.
There is therefore a great and still unsatisfied need for a multiple cavity RKA operating at X-band and higher frequencies, which satisfies the foregoing goals without significant design modifications, such that these modifications are relatively simple and inexpensive to incorporate.